1 Field of the Invention
This invention relates to apparatus for superimposing graphic title image signals (or other graphics) onto a video signal and for causing such superimposed images to scroll across the video picture derived from the video signal This invention finds ready application in so-called video titlers and telopers (or opaque projectors) and is particularly useful with video cameras of the type having an image pick-up device and a video tape recorder (VTR) housed within the same housing.
1. Description of Background Art
Apparatus for superimposing graphic title images onto video signals have been developed as peripheral equipment for use with VTR's. Such graphic title images, referred to generally as graphics, are used in video dubbing to superimpose, or insert, graphic data onto a recorded video signal. As a result, a composite video signal containing graphic information is recorded Such peripheral equipment is known to the prior art as titlers or telopers for dubbing graphic information, usually titles, onto the recorded video signals.
Typical of such graphic inserting equipment are character generators which are capable of generating various types of alphanumeric patterns. The patterns formed by such character generators appear as title image signals and are superimposed onto video signals that are reproduced from the VTR or that may be derived from an image pick-up device. However, such character generators usually are not suited for integration with presently available video cameras. A conventional video camera is a hand-held device containing a VTR and an image pick-up section within the same housing. Character generators usually are too large, too heavy and too expensive to be integrated into such video cameras.
It has been proposed to provide video cameras with the capability of inserting graphics, such as graphic title image data, into the video signals generated by the image pick-up section. One suggestion is to use the image pick-up section to image graphics which, for example, may be drawn on a screen, poster, placard, or the like, thereby generating video signals corresponding to the imaged graphics, and then storing this graphic data in a suitable memory provided in the video camera. Thereafter, the stored graphic data may be read from the memory and superimposed onto the video signal then being generated by the image pick-up section (such as the video signal representing a scene being "photographed" by the image pick-up section). The video signal then being imaged, together with the superimposed graphic data may be recorded by the VTR section of the video camera.
The graphic insertion proposal of the type just described writes graphic data into the memory on a line-by-line basis, with each line generally being divided into several image units, analogous to pixels. The location of the graphic data that is read from the memory, relative to a picture image plane, is, of course, substantially identical to the location of that graphic data when it was written into the memory. Thus, if graphic material occupied the center portion of the image plane when it was written into the memory, the graphics read from the memory and superimposed onto an input video signal likewise will occupy the center portion of the image plane. Similarly, original graphics data disposed at the bottom or top of the image plane when written into the memory will occupy the bottom or top of that same image plane when read. Likewise, graphics data located to the left or right of the image plane when written will be superimposed to the left or right of the image plane when read. Thus, the particular position of the graphic data that is imaged by the pick-up section remains fixed when that graphic data subsequently is superimposed onto another video signal imaged by the pick-up section. The user of the video camera is provided with limited flexibility in adjusting the position of the graphic data after that data has been imaged and stored in the memory. Accordingly, a noted drawback of graphic insertion apparatus of the type described above is that the graphic data that is stored in the memory cannot subsequently be scrolled horizontally or vertically, relative to a video picture, or video image plane.